The bushfires, some of which have been burning for weeks in parts of the Northern Territory and South Australia, have burned through an area larger than Belgium.
In a statement, Bushfires NT said fires around Alice Springs were causing smoke hazard to traffic.
"Motorists are urged to use care and should reconsider plans to travel on remote unformed roads," the organisation said.
"Motorists should heed all warning signs. Motorists are advised that due to potential fire threat, a number of roads are closed," it said.
The main areas where smoke is causing problems are on the Stuart Highway, Tanami Rd and the Luritja Highway.
Train services have also been affected with a freight train held up south of Alice Springs and the Ghan passenger train also facing possible delays.
Fire crews battled the fires through last night concentrating on the blaze around the tourist hot spot of Kings Canyon.
An extra 17 firefighters from South Australia joined the efforts last night.
Incident controller Sergeant Shaun Gill said cooler conditions and a change in wind direction had helped fire crews make "significant inroads".
NT fires prompt travel warnings
18:00 AEST Thu Sep 29 2011
Authorities have asked people in central Australia to
postpone non-essential travel, as 21 bushfires continue to burn.
With fuel loads at their biggest in 30 years due to unusually high rain the past 18 months, fires have caused havoc in the past few weeks in the Northern Territory.
An area larger than Belgium has burned and there has been a spike in the number of people in Alice Springs being treated for breathing difficulties.
"Ideally people should postpone non-essential travel until the fire threats abate," incident controller Sergeant Shaun Gill said.
He said the main threat was in the Henbury area, south of Alice Springs, where a large fire was burning despite back-burning and the creation of firebreaks.
Other areas of particular concern were several fires to the north and east of Alice Springs, he said.
Significant fires are burning at Bond Springs, Pine Hill, Aileron and Hamilton Downs.
"We are urging everyone to drive carefully using headlights and be alert for smoke hazards as well as wildlife and livestock on the roads," Sgt Gill said.
Train services have also been affected with three freight trains held up, one for more than 24 hours, due to the fires.
A spokesman for Genesee and Wyoming Australia, which owns nearly 5000 kilometres of railway track in South Australia and the Northern Territory, said the trains would be able to proceed once integrity tests were completed.
Grassland fire threatens Central Australia
September 30, 2011
Many parts of the nation have grass fuel loads not experienced in 30 or 40 years, on the back of heavy rains, particularly last summer.
Central Australia was in the grip of a one-in-30-year bushfire, Bushfires Northern Territory director Steve Sutton said. By yesterday, most of the fires had been contained, but authorities were still dealing with fires near Alice Springs.
Bushfire expert Phil Cheney predicted that tens of millions of hectares could burn. "It's likely to burn for months," he said.